Ferrous alloy articles having great strength at high temperatures



Patented July '4, 1950 UNITED STATES PATENT OFFICE FERROUS ALLOYARTICLES HAVING GREAT STRENGTH AT HIGH TEMPERATURES Russell Franks andWilliam 0. Binder, Niagara Falls, N. Y., assignors, by mesneassignments, to Union Carbide and Carbon Corporation, a

- corporation of New York No Drawing. Application May 9, 1946, SerialNo. 668,332.

3 Claims.

This invention relates to ferrous alloy articles operating at hightemperatures. These develop- It is the principal object of thisinvention to provide ferrous alloy articles suitable for use inapplications where temperatures above about 700 F. are normallyencountered. A further object is the provision of hot-workable andmachinable alloy articles for use at such elevated temperatures. Anotherobject is the provision of alloy articles capable of withstanding severemechanical stress at elevated temperatures above about 700 F. A morespecific object is the provision of alloys and articles wrought or casttherements demand of the metallurgist metals and alloys which willwithstand prolonged exposure to temperatures well above about 700 F. andin many instances well above about 1200 F. The problem is complicated bythe fact that severe mechanical stress is often encountered in somemetal articles used at these temperatures.

For parts of such devices as superchargers,

gas turbines, jet propulsion apparatus and the like, it is necessary toemploy alloys that are capable of withstanding severe mechanical stressat high temperatures. Depending upon the design and the intended use ofsuch devices, the

temperature ranges at which they operate may be separated .into a rangebetween 19.00" F. and about 1200 F. and into a range upwards of 1200 F.Associated parts and apparatus may be required to withstand temperaturesof about 700 F. and above. In devices operating within the lowertemperature range, generally much higher stresses are applied than indevices operating above 1200 F. In many instances it is desired thatalloys for use in such apparatus be, capable of being hot-worked andmachined, while in other in-' stances the alloys may be employed in theform of castings. In any event, the alloys must have high strength.

A number of alloys have been proposed for use at'high temperatures, butthe utility of these alloys has been limited either-because theyare nothot-workable or machinable or because they'become brittle upon prolongedexposure to high temperatures. One of the characteristics of highlyalloyed ferrous materials is that as the iron-base solid solution alloycontains more and more of the alloying metals to increase hightemperature strength, the stability of the materials at hightemperaturestends to decrease so that on prolonged exposure to hightemperatures the materials become excessively brittle.

from capable of withstanding severe mechanical stress at elevatedtemperatures above about 700 F. up to about 1200 F.

Inour copending application, Serial N 0. 599,305, filed June 13, 1945,and matured into Patent No. 2,432,614 of December 16, 1947, we havedisclosed alloys which have excellent properties at very hightemperatures, The alloys disclosed in that application contain iron,chromium, cobalt, molybdenum, tungsten and at least one element selectedfrom the group consistin of columbium, tantalum, titanium and vanadium.

The present invention comprises heat resisting articles composed ofalloys containing 10% to 30% chromium, 10% to 40% cobalt, up to 7.5%

molybdenum, 0.5% to 15% tungsten and 0.5%

to 3% in the aggregate of at least onemetal selected from the groupconsisting of columbium,

tantalum, titanium, and vanadium, the content of any single metal fromthis group being less than 2%, the remainder of the alloys being nickeland iron except for incidental impurities and small quantities ofelements customarily present in steels of good quality. The iron contentof the alloys of the present invention should be at least 10% and thenickel content should be less than 15%. The tungsten content should benot less than 7.5% in the absence of molybdenum. A generally preferredrange for molybdenum, if molybdenum is present, is 0.5% to 5%.

Carbon is always present in the alloys of the invention. Preferably itdoes not exceed about 1%, and if hot working of the alloys is desired,the maximum carbon content should be 0.35%. Nitrogen is importantlybeneficial and should be present in a proportion of 0.05% to 0.25%.Silicon and manganese may be present, the silicon content preferably notexceeding 1% and the manganese content not exceeding 2 if hot working isdesired.

A useful test for determining the suitability of materials for use athigh temperatures is the socalled stress-rupture test. In this testseveral samples of an alloy to be tested are maintained 3 at a giventemperature, each sample being subjected to a different measured stress.The time required to cause failure of the samples under these conditionsof temperature and stress is determined, and the time and stress valuesobtained are plotted'to yield a curve for the particular material undertest. From this curve can be determined the stress the material willwithstand for a given period of time, say 1000 hours, at the particulartemperature for which the curve was drawn. This test provides aconvenient method of determining the load carrying ability of a'material. It also gives some indication of whether or not the materialbecomes embrittle'd upon pro longed exposure at the temperature of thetest. A brittle material will break without elongation,

whereas ductile material will elongate before failure.

Stress-rupture tests conducted in the manner just described indicatethat the alloys of the invention maintain great strength at temperaturesashigli a's. 1"5'G0 F. and that even at such high;

a stress of2fi0tlepounds per square inch was ap plied'to severaisamplesOf the alloys to be tested while the amples were maintained eta tempera:ture of 1500* F. The time in hours'require'd'for thesarn pl to fan underthese extremely severe conditions is reported in the table; some of thesamples were in the as-forge'd condition (condition 1), others had beenforged; heated one'h'our 31151256 0; and qu'enched in water (condition2).

sound, strong and tough welds being produced without undue embrittlementof Weld metal or base metal, and such welds retain their toughness atelevated temperatures. However, if too high a proportion of any of theseelements is present in the alloys,- welds producedusually suffer fromloss of toughness at elevated temperatures.

The presence of nitrogen in the alloys of the invention within the rangeindicated is important, nitrogen having a beneficial effect on the hightemperature stability of the alloys.

The alloys of the invention are preferably worked inthe range 2100 F. to1600" F. In somecas'es working may be continued. to a temperaturesomewhat below the recrystallization temperature (about 1200 F.) Alloysso wrought are said to be in the cold hot-worked condition. They may beused in this condition in applications where temperatures not above 1200F. are encountered. For use at temperatures much above 1200F.; thealloys of the invention should be annealed at about 2200* F. to 2320 F.before use;

Beinghot-workable; machinable; w-eldable, and castable, and possessingremarkable strength at elevated temperatures up to about 1200 F., thealloys of the invention are particularly well suited to use inthefabrication of articles such as parts of superchargers, gas turbines,jet propulsion'a'pparatus andthelike which are required towithstandseveremechanical-stress at elevated temperatures.- T'heirfreedom from embrittlemen't upon'prolongedekposureat high temperaturesrecommends their use where dependability of; operation is essential?This applicationis a continuation-impart of Table Composition-RemainderSubstantially all Fe Hoursto Fail 4 @1500F.and

20,000 p; S: l. stress: Con- Per Per Per ler ,Per 7 Per Per. Per ditionCent Cent Cent Cent Gent Cent Cent Gent o Ni 00 Mo W -eb-- o N 2h 18"-1o 3o; 3 t 2 1 0.15 0.12 117' 142;." 18 10 3U v 3 l0 1 0.15 0:12 48' 18218- 10 30 0:5 1 0-.15 0.1-2 34 l The data in theabove tableclearly'illustr'at-e our copending.:application, Serial No. 599,305

the ability Of the alldys 0f the invention t0-Witl"1= stand largestresses at elevated temperatures for bfe loh'j'd' periods Of time"Without failure.

In manufacturing the alroys of this inventi n care'shouid'be'taken thatthe composition limits 'set forth beemsely'auhereu tbwvith r'e'gardtothe intenaeauseofnie an'o 'e' sin'ce'lhaterial Varia= tlh'lrithpreeertiene fif'the several ingredients eletrfineritai13 sheetmeuesmeeiproperties; For

example, if the alloys arete b'e'employed asease ings, the carbo'ncontefit may be as 'h'ig'h'as 1%; but if Hot-W'orkibilitiis desired, thecarbon c'dntent should be kept at a maximum of about 0:35 l preferablyshould not exceed 0.2%.

simiiany, the proportions Of molybdenum, tungsten; coiumbium, tantalum,titanium and vanadium present in the alloys aifect hot-work ability andwelolability. Toohigh a proportion of any of these elements has adetrimental effect on hot-tvorkability and weldability; particularly thelatter property. Alloys within"th'e composition liniit's' defined may bewelded readily by any of the common welding methods, for example,eleetrie arc, oxyacetylene, submerged-melt'electric welding, or solidphase pressure Welding,

filedliune 13; 1945ynow PatentNo. 2,4325 14,- issued' De'c'e seelsgis n.a a

Wec'lai'me 1 1. heatresistin g ferreu s alloy article capable ofwitns'tandin'g se er -mechanical stress at elejug-0.35% 0:05%-toh25%nitrogen; silicon in amount not exceeding '1%;' manganese in an amountnot exceeding 2%; the remainder of said alloy consistingfoff nickel andiron' except for incidental impurities such nickel content being presentin an amount less than 15% and such iron content being at least 10%.

2. A heat resisting ferrous alloy article capable of withstanding severestresses when used at elevated temperatures upwards of 700 F. forprolonged periods of time as herein set forth, said article beingcomposed of a machinable, weldable, castable and hot-workable ferrousalloy consisting of 10% to 30% chromium; 10% to 40% cobalt; to 7.5%molybdenum; 0.5% to 15% tungsten but not less than 7.5% tungsten in theabsence of molybdenum; 0.5% to less than 2% columbium; 0.05% to 0.25%nitrogen; carbon in an amount not exceeding 0.35%; silicon in an amountnot exceeding 1%; manganese in an amount not exceeding 2%; the remainderof said alloy consisting of nickel and iron except for incidentalimpurities such nickel content being present in an amount less than 15%and such iron content being at least 3. A heat resisting ferrous alloyarticle capable of withstanding stresses of the order of 20,000 p. s. i.when used at elevated temperatures of the order of 1500 F. for prolongedperiods of times as herein set forth, said article being composed of amachinable, weldable, castable and hotworkable ferrous alloy consistingsubstantially of 18% chromium; 30% cobalt; 0.5% molybdenum; tungsten; 1%columbium; 0.15% carbon; 0.12% nitrogen; the remainder of said alloyconsisting of nickel and iron except for incidental impurities suchnickel content being 10% and such iron content being at least 10%.

RUSSELL FRANKS. WILLIAM 0. BINDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,376,062 Albrecht Apr. 26, 19211,729,154 Clawson .Sept. 24, 1929 1,774,862 Wissler Sept. 2, 19302,213,207 De Golyer Sept. 3, 1940 2,244,517 De Golyer June 3, 19412,245,366 Rohn June 10, 1941 2,309,372 Wissler Jan. 26, 1943 2,397,034Mohling Mar. 19, 1946 2,398,702 Fleischmann Apr. 16, 1946 2,432,614Franks et a1 Dec. 16, 1947 2,432,615 Franks et a1 Dec. 16, 19472,432,618 Franks et a1 Dec. 16, 1947 FOREIGN PATENTS Number Country Date219,293 Great Britain May 7, 1925 308,549 Great Britain Mar. 28, 1929OTHER REFERENCES Kinzel and Franks: Alloys of Iron and Chromium,published by McGraw-Hill Book Co., N. Y., vol. II. 1940, pages 87, 88,180, 192, 194, 455.

Progress Report on NDRC, Research Project NRC-8, P. B. 39, 578, October7, 1942, pages 1-21 inclusive (particularly page 5). Declassified toopen January 28, 1946.

1. A HEAT RESISTING FERROUS ALLOY ARTICLE CAPABLE OF WITHSTANDING SEVERE MECHNICAL STRESS AT ELEVATED TEMPERATURES ABOVE 700*F. FOR PROLONGED PERIODS OF TIME AND HAVING HIGH STRENGTH AND STABILITY AT SUCH ELEVATED TEMPERATURES, SAID ARTICLE BEING COMPOSED OF A MACHINABLE, WELDABLE, CASTABLE AND HOT-WORKABLE FERROUS ALLOY CONSISTING OF 10% TO 30% CHROMIUM; 10% TO 40% COBALT; 0% TO 7.5 MOLYBDENUM; 0.5% TO 15% TUNGSTEN BUT NOT LESS THAN 7.5% TUNGSTEN IN THE ABSENCE OF MOLYBDENUM; 0.5% TO 3% IN THE AGGREGATE OF AT LEAST ONE METAL SELECTED FROM THE GROUP CONSISTING OF COLUMBIUM, TANTALUM, TITANIUM AND VANADIUM, THE AMOUNT OF ANY SINGLE METAL SELECTED FROM THIS LAST NAMED GROUP BEING LESS THAN 2%; CARBON IN AN AMOUNT NOT EXCEEDING 0.35%; 0.05% TO 0.25% NITROGEN; SILICON IN AN AMOUNT NOT EXCEEDING 1%; MANGANESE IN AN AMOUNT NOT EXCEEDING 2%; THE REMAINDER OF SAID ALLOY CONSISTING OF NICKEL AND IRON EXCEPT FOR INCIDENTAL IMPURITIES SUCH NICKEL CONTENT BEING PRESENT IN AN AMOUNT LESS THAN 15% AND SUCH IRON CONTENT BEING AT LEAST 10%. 